1. Field of the Invention
The present invention relates to transmitters applicable to touch sensitive panels, and more particularly, to a set of transmitters which transmit signals concurrently.
2. Description of the Prior Art
Touch sensitive panels or screens are important human-machine interfaces, especially on consumer electronic products like portable phones, tablet PCs, or Personal Digital Assistances (PDAs). Touch sensitive screens are one of the main input/output (I/O) devices. Since capacitive touch sensitive screens, especially those of projected capacitive types, are very sensitive to finger touches, it has become one of the main design choices for touch sensitive panels/screens on the market.
Touching the screen with the tip of a finger will inevitably block part of the screen, such that the user cannot confirm a point that is being detected by the touch sensitive with his/her eyes. In addition, one cannot have as accurate control as using a pen (or stylus) when using their finger tip(s) to write. Therefore, in addition to using the finger tips to touch the screen, the user may also wish to use a stylus for input to the screen.
Generally, the touch area on a touch sensitive screen made by a stylus is much smaller than that made by the fingertips. For capacitive touch sensitive screens, it is a challenge to detect the capacitive changes caused by a stylus. In particular, in many professional graphics or typesetting application environments, a lot of functional buttons needs to be added in designing a stylus. In view of this demand, the touch sensitive screen not only needs to detect the tiny tip of the stylus, but also needs to determine whether these buttons are being pressed. Under certain circumstances, in addition to detect a single stylus, the touch sensitive screen needs to detect a plurality of styli concurrently writing or drawing thereon.
In summary, there is a need on the market for a set of styli that support multiple function inputs, thereby allowing a touch sensitive screen to detect a plurality of styli while detecting the statues of the functional buttons of each stylus.